1. Technical Field
The present invention relates to an ink jet recording ink and an ink jet recording system.
2. Related Art
Heretofore, so-called ink jet recording methods of recording images and the like by minute ink droplets discharged from an ink jet recording head are widely known.
Among the above, a method of supplying an ink to an ink jet recording head has been variously examined. For example, a method of supplying ink to a head through a tube from an ink tank containing the ink and the like are known. Some of such ink tanks have a structure such that the ink tanks can be refilled with ink, so that a user can refill the ink tanks with ink without exchanging the ink tanks (JP-T-11-504874).
As the ink for use in the ink jet recording methods, one in which a coloring material (e.g., a pigment or a dye) is dispersed or dissolved in a solvent (water or an organic solvent) has been used. Among the coloring material contained in such ink, a so-called pigment ink containing a pigment as the coloring material is known because the performance, such as lightfastness, is good (JP-A-2010-155359). Since the pigment ink is not good in fixability to a recording medium in many cases as compared with a dye ink containing a dye as the coloring material, the pigment ink contains a resin for fixing the ink.
However, for the ink tank described in JP-T-11-504874, an ink tank whose capacity is higher than that of an ink tank (e.g., usual ink cartridge) having no structure of recharging the ink tank with ink is used in many cases, the contact surface of the ink liquid surface and air (i.e., area of a gas-liquid interface) becomes large within the ink tank in some cases.
Thus, the evaporation amount of the moisture increases near the ink liquid surface. Therefore, when the pigment ink described in JP-A-2010-155359 described above is used, an aggregate resulting from the resin contained in the pigment ink is likely to be generated near the ink liquid surface in some cases. When the aggregate is generated as described above, the aggregate blocks the head, for example, so that poor ink discharge is likely to occur.
On the other hand, the ink tank described in JP-T-11-504874 described above is one in which air (air bubbles) are likely to be mixed into ink due to the configuration thereof.
Specifically, the ink tank described in JP-T-11-504874 has an air hole and has a structure such that when the ink in the ink tank is supplied to the head, air is introduced into the ink tank from the air hole. In particular, when the air hole is provided at a position where air is introduced into the ink tank through ink, air (air bubbles) is likely to be mixed into the ink.
When refilling the ink tank with ink, air (air bubbles) is likely to be mixed into the ink in the ink tank.
The air bubbles mixed into the ink as described above are usually discharged above the ink liquid surface in the ink tank. However, when an aggregate is present in the ink, the air bubbles in the ink adhere to the aggregate to stay in the ink. In such a case, the air bubbles in the ink are introduced to the head to cause poor discharge in some cases.